1. Field of the Invention
The present invention concerns the fabrication of electrolytic capacitors and, in particular, the fabrication of capacitors in the form of surface-mounted chips.
2. Description of the Prior Art
There are several types of problems currently encountered in the fabrication of electrolytic capacitors.
A great apparent surface has to be developed on the anode to have a high capacitance in relation to volume.
The operation of impregnation by an electrolyte should be compatible with the technology used, the supply voltage desired and the climatic category envisaged for the components.
For SMC (surface-mounted component) type capacitors in particular, it is sought to obtain the highest possible capacitance in relation to volume and, hence, to reduce the inactive parts of the finished product. Since the impregnation is done on the oxidized part of the anode but should not go over on to the non-oxidized part which is electrically connected to the anode connection, it is sought to reduce the length of the oxidized part of the anode which is not impregnated and therefore capacitatively inactive. However, reduction of the inactive part is limited because of the short-circuits which may occur in this area. The existing tolerances with respect to oxidation and impregnation levels require a certain safety margin to be retained. This is a very essential point and is difficult to resolve except to the detriment of the total volume of the capacitor. For either aluminum or for tantalum capacitors, the minimum inactive volume enabling proper insulation to be provided between the electrolyte and the non-oxidized part of the anode is, according to prior art, a quantity between a quarter and a half of the total volume of the finished product, depending on the format. Retaining of such large safety margin restricts the miniaturization of the components or, similarly, reduces the range of capacitance that can be set up in a given volume.
In the prior art manufacturing methods, the complete anode of the capacitors is treated by insulating oxidation to produce an element that is ready to be impregnated and clad use. For this purpose, this element is transferred to final connections (wire or lead-frame) of use, on the anode or cathode side, to enable soldering or its transfer to a printed circuit.
In order to overcome the problems of electrical insulation while increasing the capacitance in relation to volume of the electrolytic capacitors, it is an object of the present invention to provide a connection strip for SMC type electrolytic capacitor anodes as well as a fabrication method that enables the elimination of a standard operation of transferring a terminal anode connection to the product and, at the same time, the elimination of the deterioration in the insulation, or possible short-circuiting.